Short synthetic glycopeptides successfully induce antibody responses to carcinoma-associated Tn antigen

Glycopeptides containing a tumor-associated carbohydrate antigen (mono-, tr i- or hexa-Tn antigen) as a B-cell epitope and a CD4(+) T-cell epitope (PV: poliovirus or TT: tetanus toxin) were prepared for immunological studies. Several Tn antigen residues [FmocSer/Thr (alpha-GalNAc)-OH] were successive ly incorporated into the peptide sequence with unprotected carbohydrate gro ups. The tri- and hexa-Tn glycopeptides were recognized by MLS128, a Tn-spe cific monoclonal antibody. The position of the tri-Tn motif in the peptide sequence and the peptide backbone itself do not alter its antigenicity. As demonstrated by both ELISA and FAGS analysis, the glycopeptides induced hig h titers of anti-Tn antibodies in mice, in the absence of a carrier molecul e. In addition, the generated antibodies recognized the native Tn antigen o n cancer cells. The antibody response obtained with a D-(Tn(3))-PV glycopep tide containing three alpha-GalNAc-D-serine residues is similar that obtain ed with the Tn(6)-PV glycopeptide. These results demonstrate that short syn thetic glycopeptides are able to induce anticancer antibody responses.